Development of the lipid bilayer membrane as an assay for ion-conductance inducing materials isolated from natural cell membranes, and study of the physical mechanisms for ion transport. The bilayer membranes are formed from natural membrane extracts, oxidized cholesterol or pure lipids in an aperture between two electrolyte solutions. The electrical properties of the membranes are measured before and after application of an activating factor such as EIM (a bacterial protein which induces excitability), hemocyanin or dopamine-Beta-hydroxylase. The first phase of lymphocyte mediated lysis of target cells is studied by observing conductance changes induced by lymphocytes in an antibody coated antigenic lipid bilayer membrane. Development of fluorescent dye-containing lipid bilayer vesicles as an assay for vesicle-cell fusion. The vesicles are incubated with human peripheral blood lymphocytes, and the resulting fluorescence is observed by microscopy, by fluorometry and by use of the fluorescence-activated cell sorter.